1. Field of the Invention
The present invention relates to a communication control processor which is capable of simultaneously creating plural data links on one transmission line, and stores data related to each link by making use of a CAM (content addressable memory).
2. Description of Related Art
FIG. 1 is a block diagram illustrating such an arrangement of a user terminal as shown in CCITT recommendation I.430, in which reference characters TE.sub.O .about.TE.sub.n designate terminal equipments including a telephone, a facsimile and the like, respectively. The terminal equipments TE.sub.O .about.TE.sub.n are connected to a control processor 10 through a user bus 30, respectively so that the control processor 10 can terminate a user line 40 such as a telephone line as well as it can control data transfer through the user bus 30.
In the CCITT recommendation, there are two systems of data signal for the terminal equipments and one system of various kinds of control signal in a basic interface of the user line 40. Further in the CCITT recommendation, since the maximum eight terminal equipments TE.sub.O .about.TE.sub.n are capable of being connected to the control processor 10 if those terminal equipments TE.sub.O .about.TE.sub.n carry out simultaneous communication via the user bus 30 having two systems of data signal, own data corresponding to each terminal equipment must be set so that plural logical data links can be simultaneously created on a pair of signal lines by time sharing processing or the like based on those own data. Therefore, it is necessary to provide one system of control signal in order to control the data transfer to and from each terminal equipment.
In the control processor 10, own data of each data link and one or plural sets of system parameters, that is, values which decide such communication conditions as transmitting and receiving states, the number of transmitting data, and the number of receiving data, are stored in a specific area of a system memory to be related with each other. When the data link is created, communication processing is undertaken by retrieval of a data link in the memory so as to read the system parameters related to the data link while software processing is undertaken by updating the system parameters so as to be returned to the system memory.
In the conventional communication control processor of such constitution as described above, when reading the parameters related to the data link to undertake the communication, all own data of the plural data links capable of being created on a transmission line and one or plural sets of parameters related to each data link stored in the system memory are accessed and then the whole area of the system memory where the parameters being stored is sequentially retrieved so as to access the own data of the required data link, which, however, results in necessitating a long time. As a result, there has been a disadvantage that when the retrieval is carried out, the bus is busy for so long time that it is difficult to realize communication control at higher speed.
In addition, irrespective of the number of the data link actually to be created, there must be ensured in the system memory a memory area in which both the own data of all the data links capable of being created and the system parameters can substantially to be stored, as a result, there has been another disadvantage that the communication system is to be uneconomical.